Generation of Multiple Modes Microwave Vortex Beams Using Active Metasurface

In this letter, an active metasurface for vortex beam generation is proposed. This metasurface can transform the incident plane wave into beams carrying orbital angular momentum of three different orders. This active metasurface is composed of an array of varactor diodes loaded unit cells. The transmission phase of each metasurface unit cell can be fully controlled by the capacitance of the varactor diodes. Different modes of vortex beams can be separately generated by simply changing the transmission phase distribution on the metasurface aperture. The properties of the proposed active metasurface are demonstrated by simulation and measurement results, which have a good agreement with each other.